You need to consider your data that is either
- stored that you would only want authorised people to access and for it to remain uncorrupted and unchanged over time
- in transit, maybe over a network (wired or wifi), vpn, by email, file transfer or even a disc in the post where you don’t want anyone except the recipient to read or change it in any way.
Hard disk encryption software is easily available (eg ESET) that meets commercial confidentiality standards which can encrypt a whole or part of a hard drive and attached devices like usb. Individual files can be encrypted before transmission.
Often email systems like Office 365 are encrypted but webmail can be more open (Google for example scan emails to enable relevant adverts to be shown). One of many solutions is mailvelope: