Colic does seem to be used as a bit of a catch all as no one really knows what causes it.
Officially, it is only colic if the baby has prolonged periods of unsettledness / crying for at least 3 hours a day, 3 days a week for 3 weeks. It usually starts at about 3 weeks and clears up by 12 weeks. It can affect both breast fed and formula fed babies but can be worse when the baby is ff due to digestion issues.
There is no cure, although anecdotally, cranial osteoptahy can work and there is apparently a study due out later this year which indicates good results for colic.
Possible causes of colic include a mild lactose intollerance which Colief can help with. Colief contains lactase which helps to break down lactose until the babies digestive system can cope with it.
Also wind which Infacol / dentinox helps with. Infacol contains simeticone as it's active ingredient which makes the wind form bigger bubbles making it easier to pass - it's adult form is Windeze. Simeticone is not absorbed into the blood stream in any way which is why it is suitable from birth. Gripe water is the natural version of the remedy with the Dill, Fennel, Ginger and Chamomile doing the same job as the Simeticone and also acting as a soother - these have all been used a soothing, gas relieving remedies for years.
IMO colic can be one, both or none of these with other unidentified factors thrown in (tiredness, over-stimulation, general overwhelm with being new to the big wide world)
Reflux is slightly different and is to do with immature valves which usually results in a very sicky baby which suffers a lot of pain and uncomfortableness when lying on their backs. Silent reflux is all of the pain without the vomiting.
Babies can have both reflux and colic, reflux without colic or just colic.