This is the 7637th most frequent Russian word.
желающие
Those who wish.
In this sentence, 'желающие' refers to people who are willing or interested in joining the excursion. It acts as a substantive participle, implying 'those who wish'.
Желающие могут присоединиться к экскурсии.
Those who wish can join the excursion.
Here, 'желающие' again refers to individuals who are interested in participating in the learning activity. It describes a group of potential participants.
Объявили набор для желающих научиться рисовать.
A class was announced for those who wish to learn drawing.
In this usage, 'желающие' identifies the attendees who had the desire to come to the event. It generalizes to people with the intention to participate.