Difference between IMPLICIT and EXPLICIT tags?

When using BER (BASIC ENCODING RULES) or DER (DISTINGUISHED ENCODING RULES), data for types are encoding using a Type-Length-Value format. Each primitive ASN.1 Type such as INTEGER has a UNIVERSAL TAG assigned by the ASN.1 standard. If you have just

A ::= INTEGER

This has a tag of UNIVERSAL2, so an encoding of the interger value5 in BER would be in hex020105.

B ::= [2] IMPLICIT INTEGER

For B, with an implicit tag, this says to replace the existing tag on INTEGER with [2], so the encoding in BER of the value5 would be in hex820105.

C ::= [2] EXPLICIT INTEGER

For C, with an explicit tag, this says to add [2] in front of the existing tag, so the encoding in BER of the value5 would be in hex A.