Monerujo is an open source wallet built by the monero community for storing monero coin. It must be noted that the wallet is not official wallet of monero. The wallet has some features which makes it compartible with the vision of monero team.
The wallet is lightweight, which means the user doesn't need to download the entire software of monero but only a part of it, so it do not take large space on the device of the user. During the transaction the wallet will use remote node to synchronize with the monero network.
The wallet is so simple to use as it poses not difficulty for beginners, the private key is also at the level of the users and the transactions within the wallet is carried out anonymously.
Since it is open source and the community of monero continue to work on it, I believe it will be a great wallet for storing monero in the future but for now it must be use with caution.