Summarize this article in one sentence.
Not everyone has gone fishing before, but most people understand how fishing works, which can make this metaphor helpful. Compare different parts of SEO to different parts of fishing. If your client wants to attract lots of people to his or her website, he or she will need lots of content. Similarly, if a fisherman wants to catch a lot of fish, he will need a lot of bait. If he does not have a lot of bait, he will not catch a lot of fish. Content will include things like:  Titles, paragraphs, product descriptions, summaries—basically anything that is written. Images, pictures, videos, and any other media content. Links and multiple pages. The better content your client's website is, the more visitors he or she will receive. Similarly, the better quality bait a fisherman has, the more fish he will catch. When going fishing, the type of fish the fisherman is trying to catch will determine where he will go fishing and what bait he will use. For example, a fisherman looking to catch tuna will not go to a river or lake, he will go to the ocean. Similarly, your client needs to know where to find his target audience, and advertise there. For example: If your client is a car repairman specializing in antique cars, he won't find much traffic in websites centered around women's makeup, hair, and nails. He would want to advertise in a local newspaper instead, or websites selling antique cars. Fishermen know where to cast their fishing line, and your client should know where to advertise his or her website. A fisherman cannot catch fish without physically being at the lake, river, or ocean. Once there, he cannot catch a fish at the other end of the river, or the other side of the lake. Fishing rods can only cast so far, and attempting to do so may result in a tangled fishing line. Similarly, your client should try to target local clients instead. For example: There are lots of people who specialize in painting houses. If your client tries to target a general audience, his website will get lost amongst the other websites. Instead, your client should try to target clients in his town, city, or suburb. A fisherman going fishing for tuna will not be looking to catch other fish. He wants only tuna, and gets a special fishing pole, a large boat, and special bait in order to catch lots of tuna. Similarly, your client needs to know his or her audience, and create a website that is popular with that sort of audience. For example: If your client's website is targeted towards teenagers, he or she will want to use more color and images. He or she will also have to consider language; something written using short, upbeat, and catchy sentences is more likely to keep a teenager's attention than long, rambling paragraphs, filled with complex, overly-descriptive sentences.
Consider explaining SEO with a fishing metaphor. Compare content to bait, and people to fish. Compare keywords to the quality of the bait. Compare your client's target audience to specific fish. Compare where your client advertises to fishing spots. Compare your client's desired audience to a fisherman's desired fish.