General maintenance does exactly what it says on the tin - generally maintaining things. Many jobs in general maintenance are fairly low key and, whilst not necessarily easy, definitely things that could be done by a lot of the population without too much training or experience.
General maintenance would tend to include minor repairs to buildings or fences, replacement of damaged items such as lights and general improvements to public property like the painting of benches. Pay in this sector would not often be well paid at all and would often be the domain of students looking for casual work or elderly people en route to retirement but still keen to be out and about and earning money.
There are some areas, such as electrical or plumbing, that would require specialised knowledge, so anyone looking to move into this sector would possibly find it useful to have done a course in a practical skill. One area which would be useful for someone in general maintenance would be caretaker. They would be responsible for some cleaning, minor repairs to property and replacement of damaged or broken lights etc. Pay isn't often too bad and, apart from a CRB check, there aren't many qualifications required. A number of major corporations have on their books a general handyman. Again, the roles would include cleaning, fixing and replacing.