Presenting is when a woman holds her body in a position that makes it easy for her partner to enter her for sex. Often this means being bent over with her ass towards her partner, or lying on her back with legs (or labia/butt) spread wide open.
Summed up by the phrase: "You want it? Come and get it!"
See take your pick for when multiple women are presenting a choice.
For presenting an actual gift or item, see gift, giving, or incoming gift.