Alpha testing is the earliest stage of external product testing, conducted with internal users, a trusted external group, or design partners under NDA before beta. It widens the audience and surfaces fundamental design and functionality issues while the product is functional but expected to be rough. Design partners are typically willing to use early-stage software in exchange for input and influence over the roadmap.
The classical alpha-beta-GA sequence: alpha (internal or tiny trusted group, software is barely stable, expectation of frequent crashes and missing features), beta (wider external audience, software is mostly stable but not yet complete, expectation of bugs in edge cases), general availability or GA (full public ...