That's "The I-10" for you younger folks. And HOT means "High Occupancy Transit" lanes. If you're driving the San Bernardino Freeway between the 605 and downtown, you have the option of taking the new HOT lanes. You can drive in there if you're a carpool (2 people most of the time, 3 people during rush hour) or if you're willing to pay an additional toll.
Regardless of how many people are in your car, you need a transponder to drive those lanes. You can get them at a discount if you're an AAA or Costco member. Visit their webpages. Or go to www.mta.net and pay full price.