Characters:
Characters are abstract entities that can be represented using a number of different character schemes or code pages. For example, Unicode UTF-16 encoding represents characters as a sequence of 16-bit integers, while Unicode UTF-8 encoding represents the same characters as a sequence of 8-bit bytes. The common language runtime uses Unicode UTF-16 (Unicode Transformation Format, a 16-bit encoding) to represent characters.
In php, under UTF-8 encoding, one Chinese character occupies 3 characters, and under gbk encoding, it only occupies 2 characters.
Byte (Byte):
Byte is the unit of transmitting information over the network (or storing information on the hard disk or memory).
Application:
If the table in the database is UTF8 encoded, and the field is set to a maximum of 10 characters, the maximum storage length is eg: 'I am 1'