ENIAC was the the first ever electronic, programmable, general purpose, digital computer that made it to be an actual machine for public use. Though it was definitely not the first electronic computer, its competitors never made it into public use, either staying as experimental prototypes or ultra top secret projects.
ENIAC wasn’t a computer you could put into your pocket and take home: it weighed about 27 tonnes, consisted of 42 sheet steel panels 2.7 m (9 ft) high and 33 cm (1.1 ft) thick, covered 167 sq m (1,800 square feet), and had its own dedicated power line feeding it 150 kW of electricity to power its 18,800 vacuum tubes. It also had 70,000 resistors, 10,000 capacitors, 1,500 relays, 6,000 manual switches, and five million soldered joints. No, you would literally work in that computer.
ENIAC had no way to store programs, so it had to literally be rewired for every new task. This was done by a crew of female operators (the world’s first computer programmers) who would pull and re-plug cables and set switches for each new set of calculations. It took days to program ENIAC and weeks to debug.
(Trivia: Who were the first ever computer programmers? Kay McNulty, Betty Jennings, Betty Snyder, Marlyn Wescoff, Fran Bilas and Ruth Lichterman.)
For more about ENIAC and what followed, read the article in New Atlas.
It wasn’t until the invention of the transistors (invented in 1947, announced in 1948; John Bardeen, Walter Brattain and William Shockley jointly shared the Nobel Prize in Physics in 1956 for inventing the transistor) which replaced the glass vacuum tubes, and then the integrated circuit (Jack Kilby at Texas Instruments and Robert Noyce at Fairchild are both credited with having invented the integrated circuit in 1958 and 1959) that computers started to become miniaturized.