Exocytosis:The process where cells transport molecules (such as proteins) out of the cell via vesicles that merge with the plasma membrane.
Endocytosis:The process where cells absorb molecules (like proteins) from outside by engulfing it with their cell membrane forming vesicles inside called endosomes.
Vesicle Fusion: The joining together or merging of vesicular membranes often facilitated by SNARE proteins.