Epiphone is a subsidiary company of Gibson that belongs to the "Chicago Musical Instrument Company. It sells guitars and basses.
Epiphone was in the early days a family concern. Everything started in Greece where Anastasios Stathopoulos built his first instrument in 1873. 1877 his family moved to Turkey, 1903 they were banished out there so they moved to the USA. Arrived in America their familyname loses an "s" because the office mad a mistake. Their "new" name is "Stathopoulo". They earn their money in america with building violins. After his dead in 1915 his sons Epimanondas (Epi) and Orpheus (Orphie) continue the company. 1917 they start to provide their instruments with the writing "the House of Stathopoulo". 1923 they start to build high-quality banjos with the label "Epiphone". It's not clear where the name comes from, but there might be a connection of the pre-name "Epimanondas". but this is only a assumption. In 1924 the concern patents the brand "Epiphone". 1925 they buy the firm "Favoran Banjo Company" (Long Island City) and they start to produce banjos under the name "Epihone recording". In 1928 the name of the family concern is officially changed into "Epiphone Banjo Co." 1931 they start to build Archtop-guitars and get in competition with Gibson. As a result, Epiphone is the only concern that made it from banjo- to guitarproduction. Epi Strathopoulo dies because of leukemia. The other both brothers Orgie and Frixo take over. But they argue and therefore Frixo sells all his possession of the company.
1945 - today
After the war, hard times descend upon Epiphone. They sell only few instruments a year, mostly contrabasses and the „Harry Volpe Model" guitar. In 1953 the next problemes arrive: the company leadership and the laber union argue, and finally the company was sold to the "C.G Conn Company" and the production moved to Philadelphia. Under some wired cicumstances two years later becomes the family Strathopoulo the company back. But because of lack of customers and workers they don't produce many instruments. Another two years later the "Chicago Musical Instrument Company" buys Epiphone for only 20.000$ (!). These company owns also a firm called "Gibson Guitar Cooperation". In fact, the biggest rival for gibson on archtop guitars is broken. In the times after the new "management" wants to keep the label "Epiphone" sustaining and so they simply mix the Epiphone guitarparts with Gibson guitarparts and sell them as usual "Epihpones". In 1961 there aren't any original Epiphone-factured parts anymore and so Epiphone is only a label for Gibson guitars. This works up to 1969 but then the production moves to Japan, but this production site is also to expensive and so the production moves to Korea. Since 2000 there are also facturies in China and since 2002 in Qingdao there's a Gibson factory that also produces Epiphone guitars. So you can say that the Epiphone guitars produced in Korea are "authorisized Gibson copies" and the ones produced in China are even "original" Gibson guitars, but produced in China. (like fender american / mexian strat). Epiphone produces also basses and - not only copies of Gibson models but also own model lines.
Epiphone - Gibson the same?
Although you can hear a lot of people say that an Epiphone guitar is the same one than an comparable Gibson model, there are some differences:
In general Gibson Guitars have better, longer stocked and more noble woods and mechanics-material.
In general in a Gibson guitar there are other pick ups.
In general they're produced in other countries.
In general they have a better workmanship
Higher price ;)
I wrote in front of every point "In General" because it's for sure possible to get an Epiphone guitar with very noble wood, workmanship etc but: If you get a very good Epiphone guitar it might be luck (I do not want to say that Epiphone guitars are bad!), because on Gibson guitars is - how to say it - putten more care when making them and on Gibson guitars you have a lot of less fluctuation between 2 guitars of the same line.
So you want to know where your Epiphone is built and when? Every Epiphone guitar / bass has a serial number on the back of the headstock. It starts always with a letter: I, U, P, R and S = Korea
EA and EE = Gibson factory in China DW, MC, SJ, Bw = China "normal" fabrique B = Czech Republique F = Japan
Then the number continues with a bank of letter that mean the following. The First digits means the year; a 5 would be 1995, a 05 => 2005. The next digits tell the month your guitar is produced All the other digits build the serial number
Example: DW8071234 = You Guitar comes from China [DW]; it's made in 1998 ; its made in July  and the serial number is 1234