What is this piece of foam for by my basement window?

I have a 14 year old vinyl sided house. The house has a basement and I have two small sliding windows that are recessed from the back wall of the house (they are at the top of the basement wall when looking from inside the house).

Anyway, as I said above, the window is recessed from the back of the house and partially underground. From inside today, I noticed something hanging down across the length of the basement window which looked like a thin piece of wood that broke in half. Upon closer inspection, I saw that the piece of wood was actually a thin piece of foam that lined the bottom of the recessed area of the window opening on the outside of the house (hard to explain...sorry). Above, there is wood on the underside that is unpainted, but looks to be in good condition.

What is that piece of foam for? Should I just glue another piece on there (assuming I can find one)?

Thanks!

 

Your description sounds like a mud sill gasket. It does not serve any purpose above your window. It is sometimes used between the mud sill and the foundation.

 

thanks, but I'm not sure that sounds right. The foam wasn't sandwiched between the mud sill and the foundation. It was attached to the underside of the length of the window opening. It was also cut to fit, so that it did not extend into the foundation.

I looked again last night and the 2nd window doesn't have it. Maybe it was there and fell off a long time ago, or maybe it was never there. Sounds like I needn't bother, right?