This is:
- a type of facility, like a gymnasium or hall
- a type of education institution or program
The name comes from the Ancient Greek name of a gymnasium in Athens. Lyceum is often used to refer to that type of physical location.
However, the word is also used to refer to a variety of educational programs. In Europe, many countries use the word to refer to secondary education, both commonly, and as part of proper nouns.
The usage isn’t as common in the United States, but it does appear as a unique word to name some programs: