People have sex when they get very turned on and horny. When they just keep touching each other slightly and rubbing against each other ever so lightly until they just want to rip each others clothes off. When they do this, and the man inserts his penis into a womans vagina/ass or a mans ass, or a woman inserts whatever into another womans whatever, they are having sex.
When my boyfriend arrived, I was wearing a skimpy black dress, black lacy boyshorts, and no bra. As soon as we got into his room, I pressed him against the wall and began to rub my perky ass on his cock. As soon as it got hard, I ripped his pants down and took all seven inches of it into my mouth, licking and sucking the whole thing until he couldn't stand it anymore. Forcefully he grabbed me and ripped my dress off, the sight of my round perk boobs freely bouncing and my thin, tan waist driving him wild. I sat on the bed, opening my legs, and said, "Fuck me."
He didn't hesitate to do so, coming at me quickly and entering my wet pussy easily. He fucked me hard, deep, and fast, causing me to moan with pleasure at each deep thrust. He grunted and I moaned, "Fuck me, of fuck me, yes, yes." The sight of my own tits being grabbed and him entering me driving me absolutely wild.
But he slid out of me and turned me over on all fours, and went into my vagina again from the back. He spanked me and made me moan as he fucked me, harder and harder, and I kept cumming, not ever wanting him to stop. He pushed me down so I was laying, and continued to fuck me, the penis going deeper than ever into me, causing me to moan and moan.
Finally it happened, I orgasmed and at the same time he pulled out and cummed into my mouth and on my tits. I swallowed all that I could and rubbed the rest into my smooth skin
"Oh my god, thank you," I said, and he grabbed my tits some more.