Eritrea was occupied (i.e. invaded) by a lot of countries and kingdoms, the most prominent of all being Italy, ruling the country from 1870s until they were kicked out in the aftermath of World War II, being replaced by the British. This insane interest in the country can be explained with its location (right in the middle of the Red Sea).
It was annexed by Ethiopia in 1962 in a gradual process, so gradual that apparently nobody noticed until they were a part of Ethiopia. This devolved into a war that only ended in 1991. Eritrea finally became independent in 1993. Not that it has much, besides access to the sea. Its infrastructure is not well developed, with its railway (yes, just the one) being a literal case of Break Out the Museum Piece, as 1930s-era Italian steam engines still chug up and down the mountains from Asmara to Massawa◊.
The relations of the country with its neighbors are not very good, with wars and frontier disputes ongoing (including with Yemen at the other side of the sea). With Ethiopia in particular, they're especially poor, particularly with their polarizing positions in the Somali conflict and the fact that both governments try to destabilize each other.
The population is also neatly divided between Christian and Sunni Muslim. And that would be all, thank you very much.
The Eritrean flag