Record can be seen as a line of data file or as a row of a database table. The record consists of fields. Each field can have different data type. See Data Types in Metadata.
Each record is of one of the following three types: delimited, fixed, mixed
In a delimited record every two adjacent fields are separated from each other by a delimiter and the whole record is terminated by record delimiter as well.
In a fixed record each field has some specified length (size). The length is counted in number of characters.
In a mixed record each field can be separated from each other by a delimiter and also have some specified length (size). The size is counted in number of characters.
This record type is the mixture of the two cases above. Each individual field may have different properties. Some fields may only have a delimiter, others may have specified size, the rest of them may have both delimiter and size.