What exactly do these terms mean and what are the implications for either of these?

The terms "major" and " minor" corrections can mee a whole range of things within their own separate definitions. I'll try and summarise thought as best I can. (anyone else who thinks differently please say!)

OK - Minor corrections. These can range from anything in between typos/making labels clearer/grammar, to adding paragraphs in, re-writing small chunks, adding info in the appendix, etc. Some minor corrections are so minor I known them to be optional - in otherwords permitted to remain within the final thesis. Other minor corrections are insisted upon before a final version is printed.

I got the latter, was given 3 months to do them (originally one month but I asked for 3!)They included re-writing a long sentence, adding more info (about a side of A4) about my analysis, plus amending all the typos. There were about 6 things altogether.

Now major corrections. This also can vary immensely. I have only know 2 people in a period of about 5 years get this option.

This usually involves re-writing several parts, perhaps adding another chapter in. The examiner might think that a major approach/theory has been omitted, or the methods are flawed in some way, but not badly enough to make the work redundant. Basically it's a result that says - "this research IS up to PhD standard, it's worth more than an MPhil, it's inovative and original - but it needs this extra work to make it more robust".

It's also worth stating that the 2 cases I know of had extenuating circumstances throughout their PhD's too. One was in hospital for a long period of time, the other's supervisor died suddenly while he was midway through, and the replacement took a different approach.