Gmail is a free, advertising-supported email service offered as part of Google's G Suite, with 15GB of storage, color-coded inbox filters and unsend button.
iTunes U is a dedicated section of Apple's iTunes Music Store that features educational audio and video files from universities, museums and public media organizations for free download to PCs and mobile devices.
YouTube is a video sharing service where users can watch, like, share, comment and upload their own videos. The video service can be accessed on PCs, laptops, tablets and via mobile phones.