Corporate espionage has existed since at least the 1700s, and the digital era has made it easier than ever for unscrupulous organizations to steal trade secrets or sabotage rivals in order to gain an unfair advantage. Competitors have been trying to steal secrets from others for centuries.
Corporate espionage is usually illegal, so organizations that engage or attempt to engage in it will likely focus on secrecy and deniability. This means that the tactics they use will probably be more sophisticated than usual, in an attempt to evade detection and attribution. Additionally, corporations often have large pools of resources (financial, personnel, etc) that can be leveraged by attackers on their behalf.
Most suspected cases of corporate espionage revolve around the theft (or attempted theft) of trade secrets - rival corporations probably don’t have a good reason to steal a password database, for example. The threat actor’s motivation is likely higher than average, as they will be focusing on competitors, but they may be unwilling to overextend and leave themselves vulnerable to detection.
Corporate espionage is primarily external but may incorporate internal elements in the form of rogue employees, or agents working for the threat actor.