According to the fluid mosaic model a membrane is composed of

The fluid mosaic model is composed of the phospholipid bilayer and proteins. This gives it its shape which looks like
this is the hydrophilic head
/\ /\ /\ /\ /\ /\ /\
\/ \/ \/ \/ \/ \/ \/ this is the hydrophobic tail

The heads are a phosphate molecule and the tails are fatty acids.

The mosaic part of the name comes from the different things which are part of this structure for example glycolipids, cholesterol and transmembrane protein.

It gets the fluid bit from always moving and not staying still eh moving in motion or being fluid.

Size and shape of continents