Voulez-vous coucher lavec moi ce soir what does that mean in English?

As an expression, it means, "do you want to sleep with me tonight".

Outside of this context, "coucher" means to go to bed.

For French people obviously the question "voulez-vous coucher avec moi" is not only to propose a sleepover, but reads "would you agree to have sex with me tonight"

Without any sexual innuendo, the question would have been "voulez-vous dormir à la maison?"

"est-ce qu'il couche avec elle?" = does he have sex with her?

will you get in bed with me

Voulez-vous = will you, would you

coucher = sleep

avec moi=with me