Generic drugs are not much different from their name brand successor. The drugs are carefully regulated in exactly the same way so that they can contain the same amount of active ingredient as well as be suitable in the way they are produced. They need to be just like the original.
The generic drug must be proven to be bioequivalent to the branded alternative i.e. releases the same amount of active ingredient over the same amount of time.
The differences are going to be in the presentation of the drug like a brand name drug may produce pills that have a nicer color or taste. However the generic version will usually contain a little more of the active ingredient.
There is little difference to the patient between the name brand and the generic. Both have to get through the same regulators and pass the same tests. Generics have a few advantages over the name brand pricier drugs.
The name brand is often the first of it’s type to be made and this is why the company spends a lot of money on making, testing and patenting the new drug and this is why they are more costly.
Generic drugs will have a patent once that has expired or in some cases are different enough from the original but still do the same type of job.