Access query parameters using request.args:

from flask import request

@app.route('/search')
def search():
    query = request.args.get('q', '')
    page = request.args.get('page', 1, type=int)
    category = request.args.getlist('category')  # Multiple values
    
    return f'Query: {query}, Page: {page}, Categories: {category}'

Use get() for single values with defaults, getlist() for multiple values.