Secretory vesicles store proteins and small molecules until they are signaled to release them as part of the regulated secretory pathway. While some fuse with the cell's plasma membrane, others do not.
During the secretion process, proteins and lipids move to the cell wall so they can exit the cell. Secretory vesicles play an important role in this process by storing molecules and proteins from the endoplasmic reticulum and Golgi apparatus until the cell is ready to release them.
As part of the secretion pathway some vesicles enter the cell membrane and fuse with it. However, this is not always the case with secretory vesicles. Some remain in place until the cell signals to release them. In contrast, others interact with vSNAREs, which are proteins that guide vesicles toward the right pathway, and lock into the cell membrane. They remain there until the cell signals that it is ready to release their content. Unlike with normal SNAREs, vSNAREs do not pair completely and force membrane fusion. Instead, the secretory vesicles wait for signals that come from outside the cell.
All of this takes place as part of the secretory pathway, which is the eukaryotic cells' means of releasing material from the inside to the outside. There are two ways the cell achieves this: through constitutive means that allow the cells to replenish and regulate, which involves the secretory vesicles.