An Acronym with several meanings:
Integrated Development Environment
An IDE gathers all of a programmer's tools together for convenience:
it can can edit, compile, debug and run programs.
Popular IDEs include Emacs, KDevelop, Eclipse and VisualStudio.
Integrated Drive Electronics
A generic term for various high-level controller Protocols for interfacing to BlockDevices. Examples of such protocols are PATA, SCSI and SATA. However, the term “IDE” is often (mis)used as a synonym for PATA.
In the days before the disk controller electronics were integrated into the drives, PCs had to interface with them using protocols such as ST-506.