In the United States, the word "school" explains what places we study. You can call college "school". You can refer to universities as "schools". You can use the word "school" for English language institutes, any undergraduate or graduate program, or secondary school.
In the US, after high school, or secondary school is called a university or college. College in the US is not a secondary school or secondary school. Program colleges and universities began in the 13th when students aged 17 or 18 years. The two-year college offers associate degrees, as well as certificates. College four years or university offers bachelor. Programs that offer this degree are referred to as "undergraduate" schools.
Universities are groups of schools for education after secondary school. At least these schools are colleges where students receive bachelor's degrees. Other schools in universities are "graduate/postgraduate" (also known as "postgraduate") schools where students receive an advanced degree. Therefore, universities offer undergraduate and postgraduate degrees such as masters (MA) and doctorates (Ph.D.).
You can get a bachelor's degree at a college or university. However, students in the US prefer to use the word "college" rather than the word "university" when they refer to four-year undergraduate programs and undergraduate degrees. They call terms like, "going to college" and "a college degree", when they talk about undergraduate programs at college or university.
Most "colleges" are separate schools. They are not located in universities. Some colleges are part of universities and are located on university campuses. ("campus" is a school building and neighborhood). Some colleges offer graduate programs in certain subjects. However, universities usually offer these programs. So, Americans use the word "university" and not "college" when they talk about graduate education.