Per Article II Section 1 of the U.S. Constitution:
And they [the Electors chosen by each state] shall make a List of all the Persons voted for, and of the Number of Votes for each; which List they shall sign and certify, and transmit sealed to the Seat of the Government of the United States, directed to the President of the Senate. The President of the Senate shall, in the Presence of the Senate and House of Representatives, open all the Certificates, and the Votes shall then be counted. The Person having the greatest Number of Votes shall be the President, if such Number be a Majority of the whole Number of Electors appointed; and if there be more than one who have such Majority [multiple majorities are mathematically impossible], and have an equal Number of Votes, then the House of Representatives shall immediately chuse by Ballot one of them for President; and if no Person have a Majority, then from the five highest on the List the said House shall in like Manner chuse the President. But in chusing the President, the Votes shall be taken by States, the Representation from each State having one Vote; A quorum for this Purpose shall consist of a Member or Members from two thirds of the States, and a Majority of all the States shall be necessary to a Choice.
The point is that for Biden to become president, he’ll need a majority (i.e., more than half) of the elector voting for him. Otherwise, each state will get one vote and there are more Red states than Blue states.
This matter has been discussed in a previous diary, but I had a bit of trouble following it, so I thought the exact wording might be helpful.