time specifiers are a easier (more human) way than cut options to specify points in a file.
a time specifier has the following form:
[[h:]m:]s[.ms]
where:
as you can see, time specifiers are easier to use but less powerful than cut options (which can also specify a point in a file in terms of bytes or frames/samples).
time slices are composed by two time specifiers designing a range (slice) of time:
begin-end
where begin and end are time specifiers. they can be not specified, meaning, respectively, the beginning and the end of the file.