What is a Rift valley

Help guys

A rift valley is a block of land that slides down along two (or one) fault lines.
The block of land can be termed downthrow (graben) while the upthrows/ horsts borders the valley in between

They are Mainly created by faulting while others such as the East African rift were formed by a magma blister which grew horizontally just below the crust causing tension and ripping the crust from Egypt to Mozambique

Where there's one fault line it is termed half graben