It varies in US colleges. The 101 course would often be a first semester, and 102 the second. The second year might be 103/104.
Other schools set up with two semesters (the full academic year) under one number.
Some schools use the "department name" with the number that indicates the level following, as "English 101."
Many schools appear to use a department/school number for the base with a two-digit extension to indicate the level of course. If physics is "Course VIII," the entry level physics course might be 8.01 (first course) with 8.02 following. Three digit "followers" might indicate graduate level (6.2xx)and/or elective subjects (8.4xx). Sometimes the "leading digit" in the "level extension" indicates whether it's graduate, elective, or "distribution" in nature.
(A "distribution course" is (usually) an elective from a department other than the one in which the student is majoring, and may be at a "survey" level or may just use different math. - Quantum Mechanics for Architects 8.459 or 8-457?)
There are "traditions" but no standards, and lots of variations.