A short summary or outline.

I had to look this up. It means to give a short introduction to some topic. Key word is "brief" . "Primer" --one of its meanings is that in school long ago the book kids often used was a "Primer"

I think it is a substance with response to an electrical impulse or friction. For example what is used in triggering explosives like grenades. Most likely a brief primer is something used to prevent a material from getting stained by absorbing colors or prevent metals to rust.

The basic meaning is "the first book used when teaching young children to read." A primer contains very simple sentences like "The boys played with the train. They went up the hill. They went down the hill. 'This is fun," said Billy." In an adult context, "a brief primer" means "a short, easy introduction to a technical subject." "Primer" is pronounced with a short I, rhyming with "simmer" and "dimmer." You would expect "primer" to be spelled with two m's, but it is not. (I'm sorry!) There is a completely different word, spelled the same way, but pronounced differently. It's pronounced with a long "I", like the "I" in the words "prime" or "dime." The most common meaning is for the first coat of paint on a metal surface. Normal paint would not stick well. Primer is a special paint that looks ugly, but sticks well. After a coat of primer, the painter puts on a second coating of the real paint.