In order from left to right,
Year in the form YYYY-MM-DD
Month in the form YYYY-MM-DD
Day in the form YYYY-MM-DD
The ISO states the 10 character format is suggested but there are options, such as the year can be displayed in two character format, the dashes don't have to be used and actually, only the year or month or date can be displayed singularly or with only one of the other two.
T used to indicate "Time will follow", if date and time are stored on the same line and field
Hours in the form hh:mm:ss
As is the case with the date, the 8 character format is suggested with the colons being separators. However, virtually everything is optional. A tenths, hundredths and thousandths of seconds field is optional after the seconds. You really don't have to use the colons, or display the hours, minutes or seconds if not needed. If the time is UTC, a capital Z is used after the time, no space between, however spaces are optional.
UTC Offset of Hours
If the time is not UTC, then the number displayed immediately after the time, is the time offset, positive or negative, from UTC time. Spaces should not be used to separate, however spaces are optional.
This all goes to show that even though this is ISO 8601, which more or less replaced RFC 1123, TANS (there ain't no standard)!