This is a type of endocytosis where large particles, such as bacteria, are engulfed by the cell. It's like if your mail carrier had to deliver a huge package that couldn't fit through the door, so they have to bring it in piece by piece.
This is another type of endocytosis where the cell ingests extracellular fluid and its dissolved solutes. Imagine your mail carrier bringing you a bottle of water with some dissolved minerals in it - that's pinocytosis!
This is a specific form of endocytosis involving the use of specific binding proteins in the cell membrane. It's like if you ordered something special online and only your signature can accept this package from the mail carrier.