A coat of primer is commonly used for many painting projects on old wood, new drywall, painted brick, bare metal, etc. to provide a consistent foundation before you apply the topcoats so that the final coverage seems much better. Accordingly, primer is supposed to prevent mold and discoloration from ruining the finish thanks to its stain-blocking properties.
To do so, you need to understand different primes to use them separately or together according to your painting projects.
For example, if you want to use oil-based paint for your work, use an oil-based primer, meanwhile, in the case of Kilz over armor textured, you should use latex-based primers to make the painting more impressive.