Is USDC the same as USDT?

I'm a bit confused about the differences between cryptocurrencies. Could you please clarify for me if USDC and USDT are the same thing? As I understand, both are stablecoins pegged to the US dollar, but are there any significant distinctions between them? For instance, do they have different issuers or do they operate on different blockchain networks? I'm trying to diversify my crypto portfolio and want to make sure I understand the nuances between these two options. Thanks in advance for your assistance!