For engineering graduates in India, GATE is usually discussed as a route to a postgraduate degree. It is also the most common filter for engineer-trainee jobs in public sector undertakings (PSUs).
GATE is conducted by the IITs and IISc and gives you a score valid for a limited period. Each PSU then publishes its own advertisement saying which GATE year and which papers it accepts. A good score with no application to the PSU gets you nothing. You must apply to each company separately, usually while GATE applications are open or soon after the result.
The list of PSUs using GATE is not fixed. Companies in power, oil and gas, and heavy engineering have recruited this way for years, but some skip a year, some switch to their own computer-based test, and vacancy numbers swing widely. Never plan around last year's list.
Final-year students should sit GATE in February, apply to PSUs as advertisements appear, and keep documents ready for interviews in the months after the result. Because advertisements are scattered, keep one tab on the latest PSU and government job notifications and check it weekly.
After the exam, watch for the official response sheet and answer key, then the result and score card. If you are also considering a postgraduate course, counselling runs in parallel; dates are listed with other admission and counselling updates. Interview call letters are issued like admit cards, through each company's portal.
Several PSUs and government departments hire engineers through their own tests, and state electricity and public works bodies run separate recruitments. A year in industry is not wasted either; see current private sector openings for engineering freshers and try again with experience behind you.