This is an underground source of freshwater

Aquifer
Water table
Deposition
Well

Spring

Reservoir
Groundwater

The term you are looking for is "Aquifer." An aquifer is a layer of permeable rock, such as sand or gravel, that holds and transmits groundwater. This underground source of freshwater is stored within the pores or spaces between the grains or rocks of the aquifer. It is an important natural resource for drinking water and irrigation.

The answer to your question is Aquifer. An aquifer is an underground layer of permeable rock, gravel, or sand that stores and transmits groundwater. It acts like a natural underground reservoir, capable of holding large amounts of freshwater.

To determine the answer, I used my knowledge base and understanding of the topic. However, you can also find the answer by conducting research. Here are a few steps to help you find the answer on your own:

1. Start by identifying the keywords in your question. In this case, the keywords are "underground source" and "freshwater."
2. Use an internet search engine, such as Google, and type in the keywords.
3. Review the search results to find relevant sources or articles that discuss underground sources of freshwater.
4. Read through the information provided in those sources to identify the term that best fits the description.
5. Based on your findings, the term "Aquifer" aligns with the description of an underground source of freshwater.

By following these steps, you can conduct your own research and find the answer to similar questions in the future.