Please elaborate on these chess terms

Could some one give an example of "over extended" and "sharp".

I presume the former is a pawn roller that advanced too early and "sharp" being a position that is riddled with tactics?

You are correct about both. If your center pawns are over-extended, then your oppenent can easily strike back. A sharp position is riddled with tactics, dangerous for both side.

The King's Gambit is sharp. The Sicillian is sharp (the dragon is very sharp). 

Now that I think of it, I don't believe I've seen either term defined in any book I've seen, which is surprising.

I believe your definition of "sharp" is quite close, although I think of it more as a position that can easily slip from won to lost, or vice versa, with a single misstep, especially  in a position where it's easy to make that misstep, especially a highly tactical position. In one book on the Najdorf Sicilian I bought once, there were parenthesized lines after almost every move with "?" after those moves, yet just one or two moves before or after that same move it was marked with a "!", such as "...b5? Nxb5!" then later "...b5 Nxb5? Qb6!" That's a good example of "sharp".

I believe "overextended" means "advanced too far forward to protect adequately," and could apply to anything from a single pawn (the most common) to an entire center (as in Alekhine's Defense).

If you're really interested I could search for a game with an overextended pawn for you.

How about this term -- "kettle position"

What is a "tall pawn"?

In what way do you mean by your opponent can strike back? I presume to win a pawn? If my definition of over extended is correct it's quite easy to liquidate the centre by opening it up hence why I'm a bit mift about control of the centre with, namely, e4 and d4 pawns but they don't seem to be there for that long unless it's an advanced variation of an opening which closes the game to play on the flanks.

Your definition of "sharp" by using the King's Gambit and Sicilian Defence is questionable. What if they decline the gambit and the Sicilian could become a patient positional game along the lines of QGD.

I mention "sharp" because I see a lot of players use this phrase when a move is made in some games and they're like, damn that's sharp! I don't think an opening can be used to define "sharp".

What is a "tall pawn"?

I believe a "tall pawn" refers a bishop which is placed in such a position that it's doing no more work than a pawn would do if placed in the exact same position - usually just protecting another pawn.

"Sharp" with respect to a given chess position can actually be represented with a simple diagram I invented, a diagram where you can see the degree of sharpness at a glance. I don't have the time to create such a diagram in a visual editor right now, so I'll just describe it...

If you look at a site like 365chess where it tells the percentage of wins, draws, and losses (for White, left-to-right) for a given position, something like these...

[27.3% 38.3% 34.4%] for the Exchange French

[37.4% 28.2% 34.4%] for the Najdorf Sicilian

...and then draw a rectangle partitioned into three consecutive rectangular regions such that each interior rectangle touches the bottom of the outer rectangle, then you can make the width of each interior rectangle correspond to the percentages shown. The central rectangle then represents the drawishness of the opening, in some sense, as if you were looking at a knife blade along its edge. If that "blade" (central rectangle) is tall and thin, i.e., if the blade is "sharp," that means the position tends to be decisive, producing relatively few draws and favoring a decisive outcome for one side or another. If the blade is relatively wide, i.e., if the blade is "dull," then it's a drawish opening, the opposite of sharp.

For example, note in the above statistics that the Exchange French has a 38.3% width (over 1/3rd of the total width of the outer rectangle) for draws, versus 28.2% width (less than 1/3rd of the total width of the outer rectangle) for the Najdorf Sicilian, which means the Exchange French isn't as sharp as the Najdorf Sicilian. In the diagram the blade for the Exchange French is wider (duller) than the blade for the Najdorf Sicilian.

P.S.--Here's a good example of a very "sharp" position: few or no draws, corresponding to a narrow or nonexistent central gray region, flanked by green and red regions each close to 50% of the full width:

Correct.  

Still waiting on the "kettle position". Hint: it's very common, so it would be nice to know its name.

When I think of the word Kettle it reminds me of the word Cuddle.

Thus, Cuddle position would be holding someone gently, very tight, for long periods of time.

They can strike back to gain center control and/or dispute the center control of the opposition.