Meaning a lack of experience when referring to "the bases."
1st Base) French - Kissing. Usually with tongue.
2nd Base) Feel - To cop a feel, grope, or fondle.
3rd Base) Finger - Sexual stimulation using the hands. Oral sex could take place after this point.
Home Plate) Fuck - Sex, intercoarse.
Baseball is being used as a metaphor for intimacy. In baseball, if a player is on the bench they are not in the game.
"So, Evan, how did things go with Erica last night?" said Ben.
"It was pretty chill, man. The movie sucked though." Evan replied.
"Did she let you cop a feel at the movie?"
"Dude, I'm still on the bench."
"That was like your fifth date. Shouldn't you be getting a little action by now?"
"Naw man, we're taking things slow."