“The law” governs every aspect of our lives. The things you do which may be criminal, your rights as an individual, formal obligations to others, the way in which you own land, how you earn money/pay tax, the way companies operate, the way in which you resolve disputes, how you dispose of property on death etc etc. One could go on for hours.
When you study law as a subject, you take those individual topics and analyse them in detail. Taking my examples above, those would constitute modules in criminal, human rights, contract, property, employment, tax, corporate, litigation, wills/probate respectively. Some of those you’re more likely to cover on the legal practice course than on a law degree.
In each of those modules, you examine different things. In criminal for example, you look at the different criminal offences and investigate the different aspects of those offences. In contract, you look at the way contracts are formed, enforced, broken and terminated. When studying any legal topic, you’ll be examining the relevant legislation and case-law and understanding why the law is what it is today, and how it should be reformed.
As you note, it isn’t necessary to do a law degree to be a lawyer. You could do a degree in history and then, before studying your Legal Practice Course with all the law grads, do a one year course known as the CPE. That route is becoming increasingly popular and many of the big London firms take a 50/50 split of law/non-law grads. The course can be expensive (others can give you a realistic estimate) and will be in addition to the 1 year you spend on the LPC. If you get a job with a big City firm (which doesn’t sound like it would be your thing) then you may get your fees and a living allowance paid for.
Hope that helps.
Chalks