These fields are designated with tags, or numbers that indicate the type of information in the field. Subfields

A subfield is a small bit of information that is apart of another piece of information. In essence, a subfield is a piece of information.

Indicators

Indicators are used in some fields to give special information about what appears in that field. Most fields contain up to 2 indicators.

Format integration

Format integration is the term that refers to "signposts" used to mark the data in records. Data is marked in records for different publications to avoid having to have varying...

A group of tags is assigned a record instead having tag sets assigned for each type of record. Format integration is used to for simplification purposes.
Delimiters

A subfield delimiter is a character used in a MARC record to "alert" the computer that the next characters in the record are going to belong to a new subfield, and it should look for the subfield code. (it makes sense to the computer, even if it seems unnecessary to us!)

Non-filing words

A non-filing word (or character as it is also called) tells the computer to ignore specified number of words and/or spaces.