Gerunds are nouns that end in ing. Participles are verbs and adjectives that end in ing.
To keep keep your writing direct and focused, aim to limit the use of gerunds and participles in all content and in technical content in particular.
Titles and UI text should favor the simple present tense (Log in instead of Logging in).
Also, when you limit the use of ing words, you avoid ambiguity and make your content easier to translate. Gerunds can have multiple meanings ("running" means different things in these sentences: I like running and The process is running). A skilled linguist will be able to tell the difference, but machine translation may struggle. So err on the side of clarity and limit ing words whenever possible.