I'd like to share with you https://words-keeper.com - web app(available in browser from any device) for foreign language learners and teachers. It lets you build your own vocabulary, keep words, phrases, notes(articles, pictures, rules, teacher's worksheets etc), create learning groups, share with other people, train.
How I use it: All words and phrases are groupped by tags. Also I have 'Notes' for different themes (e.g. 'Date and time prepositions' etc). Usually I learn by tags. E.g. today and tomorrow - 'Astronomy', after tomorrow - 'Fruits' etc. When I learn the 'Astronomy' tag, I read articles about astronomy, listen podcasts, read news on this theme, look at pictures. The main advantage of Words Keeper is that you can keep everything you learn in one place and learn everywhere.