The main vent is the main outlet for the magma to escape. Secondary vents are smaller outlets through which magma escapes. The crater is created after an eruption blows the top off the volcano
Magma chamber
central vent
crater
I think
1. The cells contain the same genes and express the same genes.
2. Multipotent (can differentiate to a limited number of cell fates/into a closely related family of cells).
3. Multipotent, totipotent, pluripotent (though I'm not 100% sure on this one).
4. Provide a source of cells for the body to replace certain types of cells that die.