It means that Tesla is the first company ever to sell 1,000,000 all-electric cars globally. For comparison, Nissan exceeded 500,000, while BYD is above 370,000 BEV cars we believe (750,000 including PHEVs) - see a comparison of the two from December 2019 here.
First, let's take a look at the cumulative production numbers, as of the end of Q1'2020:
- over 1,020,000, including 545,245 Model 3/Model Y and 1st gen Roadster.
Tesla Model S/X/3/Y Deliveries Cumulative (quarterly) - Q1'2020
Sales, as of the end of Q1'2020, exceed 990,000:
- Total 3/Y sales: about 524,970
- Total S/X sales: about 463,607
- 1st gen Roadster: about 2,450
- Total sales: over 990,000
As of the end of March, there were over 30,000 S/X/3/Y produced, ready to ship (the difference between total production and total sales). Plus, the Tesla Gigafactory 3 was producing the Model 3 at a rate of about 3,000 per week. This is why we believe that the 1,000,000 mark was reached in April 2020. It would require less than 10,000 deliveries after all.
The second million might be sold within the next 18-24 months, as the manufacturing capacity will be at around 800,000 per year soon.