Public-key encryption is slow, and awkward for data that many people need to read. The standard fix, the one this tool is built on, is to nest encryption in layers, like envelopes inside envelopes.
Encrypt the secret itself with a fast, random, single-use key. Call it the data key.
Encrypt that data key with a key belonging to the whole group. Call it the vault key.
Encrypt that vault key once for each person, using each person's public key.
Now the interesting part. To add a new team member you do not re-encrypt the secrets. You encrypt one small thing, the vault key, to their public key, and write one small file. Adding the two-hundredth person to a vault holding ten thousand secrets writes one file and takes a moment.
Why this matters to you
Some systems give every member their own encrypted copy of everything. That gets slow and error-prone fast, and it means removing someone touches every file. Envelope encryption is why "grant Alice access to production" is instant here, and why the same ciphertext works for one person or two hundred.