Phospholipids

Hydrophilic: This term refers to molecules or parts of molecules that love water and can interact with it. The 'head' of a phospholipid is hydrophilic.

Hydrophobic: This term refers to molecules or parts of molecules that repel water. The 'tail' of a phospholipid is hydrophobic.

Lipid Bilayer: This is the basic structure of a biological membrane, composed primarily of phospholipids. It forms when two layers of phospholipids align with their hydrophobic tails facing each other and their hydrophilic heads facing outwards.