Radio Frequency Identification (RFID) tech can be divided into three types depending on the power supply of tags: passive RFID, active RFID, and semi-active RFID. 
1. Passive RFID.
Of the three types of RFID products, passive RFID is the oldest, most mature, and widely used. In passive RFID, tags get a quick power boost from radio waves sent by readers and energy gained through electromagnetic induction coils to exchange info. Since it skips the power system, passive RFID tags are tiny, simple, cheap, low-maintenance, and long-lasting. But they usually have short effective recognition distances and are best for close-range contact identification. Passive RFID operates at lower frequencies like 125KHz and 13.56MKHz, and its typical uses include: bus cards, second generation ID cards, cafeteria meal cards, etc. 
2. Active RFID.
Active RFID is a relatively new kid on the block but has already become indispensable in various fields, especially in electronic toll collection systems on highways. Active RFID gets its juice from an external power source and actively sends signals to readers. It's bulkier but also has longer transmission distances and faster speeds. A typical active RFID tag can connect with a reader from a hundred meters away, with a reading rate of up to 1,700read/sec. Active RFID operates at higher frequencies like 900MHz, 2.45GHz, and 5.8GHz, and can identify multiple tags simultaneously. Its long-distance and high-efficiency make it essential for high-performance, large-scale RFID applications. 
3. Semi-active RFID.
Passive RFID doesn't need power, but its recognition distance is too short. Active RFID has a long enough recognition distance but needs an external power source and is bulky. Semi-active RFID is a compromise between these two. Semi-active RFID, also known as low frequency activation trigger technology, is typically dormant and only powers up the part of the tag that holds data, so it uses less power and lasts longer. When the tag enters the reader's range, the reader first activates the tag precisely with a low frequency signal at a small range of 125KHz, then exchanges information with it via 2.4GHz microwave. In other words, it uses low frequency signals for precise positioning and high frequency signals for fast data transmission. Its typical use case is: in a large area covered by a high frequency signal, multiple low frequency readers are placed at different locations to activate semi-active RFID products. This accomplishes both location and information collection and transmission.