I thought there was a thread on the topic I can't find it at the moment you can look for it yourself.
A quick rundown on counting
combos.
There are 6
combos of each
pair since you have 4 cards to choose from. 4c2(Read 4 choose 2). AB AC AD BC BD and CD. AB=BA since order doesn't matter so AsAh is equivalent to AhAs.
There are 16
combos of every other hand with 4 of those being
suited. We have 4 cards to choose from then 4 again so 4*4 gives us 16
combos or 4c1*4c1.
Note: 4 of these are
suited.
There are 52c2=1326 combinations of hand
Now once we see the
flop both our
range and opponents
range becomes more limited. If villains
range is
AA and 22 he has 12
combos of hands. Once the
flop comes A44 he only has (3c2)3
combos of
AA and 6
combos of 22 now. If the
flop came AA4 he would only have (2c2)1 combo of
AA.
For non
pair hands we can simply multiply as follows. If our
villain has AK and the
flop is Axx he now only has 12
combos(3*4) of AK. AKx
flop he has 9combos(3*3). AAK
flop he only has 6
combos(2*3). If we have AK and the
flop is AAK our
villain only has 2
combos(1*2).
If you need more explaining I can make a better, less rushed
post. This should be enough to get you started on thinking about counting hand combinations though.
Note: 52c2 means 52 choose 2 which is basically 52*51 / 2*1.
It's really (n)! / k!(n-k)! where n is 52, k is 2.