This is a classic example of a Spanish 'false friend' What you would call 'conferencia' in Spanish is a 'lecture' in English. This is a fairly long formal talk, usually delivered by a tutor to a large group of students. Lectures usually given in an academic context. What we call 'conference' in English might be translated as 'conferencia', but also as 'reunión' or 'congreso'. Conferences are large-scale meetings, lasting a day or several days, usually held in a business context. They are an opportunity to meet other people in your field, share ideas and make professional contacts.

No, they are quite different. A conference is a meeting. Usually people will give short talks, or show posters about research topics. Those talks will often be arranged in groups around a similar theme. The idea is that colleagues meet to present and discuss their work. A lecture is a formal talk. It is mainly educational - an expert will talk on a topic that they are familiar with. Here, almost all university classes consist of a lecture, where the teacher talks to the students about a particular topic. There are also public lectures, where again an expert will give a talk or presentation, but usually on a topic of more general interest. A lecture is typically 1 or 2 hours long.

A "lecture" is a monologue, which is normally quite long, on an academic theme. University lecturers (US: professors) give lectures to students. A "conference" is a formal meeting where different people give their opinions on the same subject. A conference may include lectures.