A marketing channel is a route by which a customer arrives. They differ in what they cost, how fast they work, and whether they keep working.
The channels a local service business actually uses
Referrals — cheapest, highest converting, hardest to scale deliberately.
Reviews and the business profile — the main source of new local enquiries for most trades.
Unpaid search — slow to build, keeps working.
Paid search — immediate, stops when spending stops.
Existing customers — the cheapest revenue available and the most neglected. Email or post to people who have already bought outperforms most cold channels by a wide margin.
Vehicle livery and signage — small, cheap, permanent.
Direct mail to a defined area, which still performs for trades where the work is tied to property.
Social media — better at staying present with people who already know the business than at finding new ones.
The mix matters more than the channel
A business on one channel is exposed to it changing: a ranking move, a platform change, a rate rise. The same concentration risk as customer concentration.
Judging them against each other
By cost per lead and, where the data supports it, by what those leads become.
That comparison depends on knowing which channel produced which enquiry, which is attribution — and it is the part most often estimated. Asking every caller how they heard of the business costs nothing and is the single most useful marketing measurement a small business can make.
Brand
The cumulative effect of being seen consistently. It is real and slow, and it shows up as better response from every other channel rather than as enquiries of its own.