The term “combinations” is mostly used when discussing either Hold’em or Omaha variants, although it can be used to describe a specific combination of cards in any variant.
There are 1326 unique combinations of two cards that can be dealt preflop in Hold’em.
There a 4 combinations of each suited hand, e.g. 7♠8♠
To calculate the remaining of a certain unpaired (preflop) hand, we multiply the number of first card remaining in the deck, with the number of the second card remaining in the deck.
By “paired” holdings in this context we are referring specifically to pocket pairs. The number of paired combinations paired in the deck is a little different.