5G UC

Short for 5G UltraCapacity.
This icon will show on your T-Mobile/Sprint 5G device running Android 12+/iOS 15+ when you connect to T-Mobile's 5G UltraCapacity network. The bands you'll see labeled under the 5G UC branding is: 5G n41 (2.5GHz MidBand), 5G n260 (39GHz mmWave), and n261 (28GHz mmWave). n77, and other mmWave bands are to come in End of 2022 or over.
With 5G UC, you may experience speeds up to 1.8Gbps (MidBand) and over 3Gbps with mmWave. You may also notice reduced latency (Ping) and will be able to stream high definition video and sound much more fluidly, with less buffer time.

A1: Look at my Speedtest on 5G UC, I got 880Mbps download, 115Mbps Upload, with a 15ms Ping, 2ms Jitter, and no PacketLoss!
A2: Cool, I don't care. But in reality, I'm jealous
A1: S u r e
A2: ...

4G LTE

The 4th Generarion of mobile wireless networking, increasing data speeds significantly from 3G, but now is slow compared to 5G.

A1: My phone has 4G LTE on full 5/5 Signal Bars
A2: I have 1/5 bars of 5G UC that's still faster, L.
A3: Sad in 3G from Verizon.