A news beat is an area of specialization that a journalist continues to follow for a few months, years or, sometimes, an entire career.
Specializations can be difficult because each has its own language and expectations. The police beat and the science beat are very different creatures, and although they may overlap, an inexperienced reporter in either area can make serious mistakes.
Fortunately, each specialization has its own educational association that serves your needs. And there are also specialized training and information resources available for each beat.
Associations usually have web sites that offer “tip sheets,” tool boxes, glossaries, and advice on covering difficult areas of the beat.
The central place for early career journalists is the Society of Professional Journalists, spj dot org, and you should become a member while in school.
Other associations are created by and for journalists, such as the Education Writers Association, the Society of Environmental Journalists. A list of these are available at the Council of National Journalism Organizations.
Still others are helpful for journalists covering the beat but are not created by journalists. For example, for help on the police beat you might consult the National Association for civilian oversite of law enforcement