I bought my Samsung Galaxy S5 online for a decent price and it's been 2 years and I still have it. It's a Samsung-SM-G900V and I was wondering can I used it internationally if I purchase a international sim card. I plan on moving to Guatemala. I'm confused whether this phone works outside the United States.
Let's pretend you are traveling to Guatemala to keep your question on-topic.
Yes. The most common frequency in Guatemala is 1900 MHz which your phone supports. They also have 850 Mhz service but your phone does not support this, so make sure you choose a network that uses 1900 Mhz such as Movistar or Claro.
According to FrequencyCheck.com, the SM-G900V (the U.S., Verizon variant of the Samsung Galaxy S5) is not compatible with the LTE (4G) frequencies in use in Guatemala, but does support the GSM and UMTS frequencies.
The frequency bands reported to be available in Guatemala are
GSM (2G) - 850, 900, 1900
UMTS (3G) - B2 (1900), B5 (850)
LTE (4G) - B2 (1900), B5 (850)
If you are satisfied with voice and 3G data, you could use the phone, once unlocked, in Guatemala with a local SIM from Claro or Movistar (which use the B2 band) or Tigo (on the B5).