Couchdb is a database system, where entries are json objects (allowing attachments), and that you can access and synchronize via simple http requests.
As explained in wikipedia:
Apache CouchDB is an open-source document-oriented NoSQL database, implemented in Erlang.
And as described in the couchdb official website:
Seamless multi-master sync, that scales from Big Data to Mobile, with an Intuitive HTTP/JSON API and designed for Reliability.
Shipped version: 3.1.1
$ yunohost app install couchdb
It’s my first yunohost package, so happy to receive feedback, and if there are any issues, you can report them here
For more info, you can also check the package readme.