I guess, as a pianist, chords are one of the things that really interest me (in common I should think with guitar players) so a jazz player needs to be familiar with chords and how to use them.
In a previous post, I was talking about the chords of the major scale, ie three and four note chords that are built up in thirds (every other note of the scale) to form chords.
Its the 4 note chords that the jazz man uses, and what makes a good pianist/guitarist is how they 'voice' the chords (in the US, they might call it how they 'spell' the chords).
Before we get to voicing chords though, some thoughts about how chords are used in a lot of tunes.
The magic sequence in a lot of jazz standards is II V I (2 - 5 - 1 NB Roman numerals are often used for chord numbers).
In C that would be Dm7, G7 and Cmaj7 (Using four note chords)
In F Gm7 C7 Fmaj7
In Bb Cm7 F7 Bb maj7
Try to work out the other 9 keys, you will find that it will be one of the most useful exercises you'll ever do!
Why? a lot of composers, especially of jazz standards used these sequences frequently very often to modulate (temporarily change key in a piece).
These sequences, especially just the II V become signposts for you to 'solo' (make up your own variation or extemporise) which of course become the real fun of playing jazz!
Best of luck with the practice, and don't forget, going on a jazz workshop will help you with all of this!