An "optical table" is to optical technologies as a solderless breadboard is to electronics.
Basically, it's a big, stable platform with lots of threaded holes of a standard size and pitch for attaching lasers, mirrors, etc. Most have some kind of pneumatic isolation or damping to keep vibrations from being transmitted from the floor. Things like interference phenomena are sensitive to displacements of a few nanometers, so you really don't want things like passing trucks to ruin your experiments!
Examples here: http://www.newport.com/Optical-Table-Selection-Guide/140219/...