Oracle Character set identification

Question

In the given export(Normal Export) log file i see following:

Export done in WE8ISO8859P1 character set and AL16UTF16 NCHAR character set

Is this multi-byte or single byte database char-set.

Can you please explain me a bit

• What is difference between multi-byte and single byte character set?
• Can we import multibyte into Single byte and vice versa?
• How can we identify weather a character set is multi-byte or single byte by looking into its name?

Please provide any other useful information on this topic?