Surnames were not known in Britain until the Norman Conquest. People were either known as 'son of' or 'daughter of' or they had a nickname. This nickname could have been based on something personal, say they had a limp, or a big nose, or stooped, or they had red hair, the list will be endless.
When the Norman barons came to Britain, they introduced the use of surnames. The British people did actually catch on to the idea, but they didn't necessarily stay with the first surname they chose. Eventually surnames were used and they stuck.
It was a lot easier in the olden days because communities were much smaller and as everyone knew everyone else your personal name was enough, because everyone would know your family as well, therefore 'son of' would be enough for identification.
A large number of people would be known by their trade, Roger the fletcher, William the smith, and so on. You would eventually end up with Roger Fletcher, William Smith, Richard Redhead and so on.
Around the year 1400 most English families and even those from lowland Scotland had adopted hereditary surnames. People were still finding new surnames to take, as immigrants came to Britain bringing new names with them.
A lot of Scottish, Welsh and Irish names derive from gaelic personal names so you need to keep this in mind when doing Scottish or Irish genealogy. The Welsh people took longer to adopt surnames, but this was accomplished by 1536 when Wales and England became united.
Family History and family tracing has been made more of a minefield by people and families changing their names in the past. Of course they would have had no idea that people in the future would be interested in who they were and what they were called. There didn't always need to be a legitimate reason, they would often do this purely because they felt like it.
Although surnames are your main area of research when looking into your family history, you need to be aware that the name could have been changed over time.
The spelling of your family names could have been so different, mostly because way back not many people were educated enough to recognise if their name had been spelt differently, or even know how it should be spelt in the first place.
Making the spelling of names standard wasn't achieved until the 19th century, but even now spelling mistakes can happen. Names cannot always be spelled phonetically, they might sound like one thing but be spelled quite differently. Take for instance the personal name of St. John, this is pronounced Sinjun. If you were not able to read and write, how would you spell it?
Surnames which evolved from place names are probably the ones which have survived the longest, and obviously they are more common because of the number of people who would have lived in that particular place. Even countries have provided surnames, French, Fleming, Britten etc.etc.
You can have names from rivers - Surtees [meaning on the Tees], Pickersgill [meaning a stream containing pike], Fleet [an estuary or a stream]. Trees also provide names such as Leaf, Root, and Elmes, Maples, and Oakley to name but a few, you get the picture.
Many of the old occupations also provided names, for instance Frobisher meant a refurbisher or cleaner of armour. Arkwrights were makers of arks or chests. Mason, Fisher, Thatcher and so on, all self-explanatory.
The study of names is something that could keep you occupied endlessly, but if you are a committed family historian, this is a very important facet of your study. By this I don't mean you have to turn yourself into a professional genealogist, but always keep an open mind and be prepared for all sorts of weird and wonderful spellings of the name you are researching.
Always take down any details you come across for the name you are currently researching, even though you may think that it is the wrong person because the spelling isn't as you expected to find it.
Better to take down the information there and then than to wish you had later on.
You need to remember when you are looking at details taken from older church registers that not all ministers were educated. Some were, exceedingly so, but others were not, and you will find many spelling anomalies in older register details.