Electroweak is the term for a generalized type of interaction between particles that encompasses both electromagnetic forces and the weak force. An electroweak force is defined such that different aspects of it show as the other two forces, allowing a single theory to explain both forces.
The concept of the weak force was formulated earlier as an explanation for some radioactive phenomena, e.g., beta decay.
The two other forces of nature besides electroweak are the strong force and gravity. Theories that extend electroweak to include the strong force are called Grand Unified Theories or GUTs. Numerous candidate theories have been developed but none have been proved or widely accepted.