The 'Sort' Command Line Program
This is frequently used for sorting input in text or TSV formats, in various different ways supported by it; which may be either lexicographical, case insensitive, based on the numeric field only, based on a particular column, etc. Using a variety of flags and options, sort can also be extended in various powerful ways. The command can also be used for sorting tables of data, delimited by commas (csv) or tabs (tsv) or even spaces; on a particular column or field. The -k option helps sort the input file on a particular field, i.e. the column number.
A few useful resources to study these variations of sort are:
A Wikipedia entry for the 'sort' command
How to Sort Files in Linux using Sort Command