A notice period is the interval between giving notice and the date employment is due to end.
When a prospective employer asks about your notice period, it is usually trying to establish when you could start. Check your terms of employment before giving a date. A contractual notice period may be longer than the minimum that applies. If you agree an earlier leaving date with your current employer, that agreement changes the date you can offer. A request about availability from a prospective employer is separate from giving notice to your current one.
In job listings
Prada’s London retail trainer listing stated a preferred start date but allowed for candidates with longer notice periods. The wording tells a candidate there is room to discuss a start date at interview.