Which English word for the person who helps travellers while travelling?

Solution 1:

There are a number of related roles

A guide or tour guide or more formally tourist guide (as mentioned) takes groups of tourists around, talking knowledgeably about history, architecture, etc. They may escort a tour group on their travels through multiple destinations, or just provide short tours of a specific city, area, or building. (Career information)

A holiday rep (short for representative) is a related job which involves providing assistance and possibly entertainment to holiday-makers and maybe arranging coach trips and transfers, but doesn't require any deep historical or art-historical knowledge. It's often associated with package holidays, beach holidays, etc. (Career info)

Another related job is a concierge, who usually is based in one place such as a hotel or a specialist concierge service, and who tells people the best places to go for whatever they want, but doesn't accompany them. (Wikipedia)

A tourist information officer does something similar to a concierge but works out of a (often publicly-funded) tourist information office and serves all visitors not just those who've paid.

Solution 2:

This is the job of a tour guide (American English) or (less commonly used in British English) tourist guide. Just guide may work too.

a person who takes people on trips through an area and explains the interesting details about it

(source: Merriam-Webster)

It can be used both for people who guide an entire multi-day trip for a fixed group of people, as well as guiding a 'random' group of visitors to a single location for a few hours.