The treason trials were a series of trials of people, mostly senators, who were accused of treason. They were mostly aimed at senators and the upper classes, and wouldn’t have significantly affected ordinary peoples’ lives. However they did foster a sense of mistrust and fear within Rome. This was compounded by those who profited off making accusations, whether true or false.
Tacitus is particularly negative about the trials due to his hatred of Domitian and his similar trials.