目錄是由人為編輯的搜索結果。大多數(shù)目錄依靠的是人為提交而不是爬行器（spider）。
Directories are search results that are edited by people. Most directories rely on human commits rather than spiders.
競價（bid）為每個搜索引擎引薦向搜索引擎支付發(fā)費用，用以保證在付費搜索結果的排名。其最簡單的形式，付費搜索結果顯示出價最高一方的網(wǎng)頁鏈接在結果列表的頂端，并且競標方每次在訪客點擊競標方的鏈接時付錢給搜索引擎。
Bidding (bid) refers to each search engine to pay a fee to the search engine to ensure the ranking of paid search results. In its simplest form, paid search results show that the page link of the highest bidder is at the top of the result list, and the bidder pays the search engine every time the visitor clicks the link of the bidder.
關鍵字、關鍵詞和關鍵描述標簽短語（Keyword、keyterm 和 keyphrase）
Keywords, keywords, and key description tag phrases (keyword, KEYTERM, and keyphrase)
關鍵字、關鍵詞和關鍵描述標簽短語是 Web 站點在搜索引擎結果頁面（也稱為 SERP）上排序所依據(jù)的詞。根據(jù)站點受眾的不同，您可以選擇一個單詞、多個單詞的組合或整個短語。為簡化起見，本文將使用關鍵詞 這個術語表示所有這三種類型。
Keywords, keywords, and key description tag phrases are the words by which a web site sorts on search engine results pages (also known as SERPs). Depending on the audience of the site, you can choose one word, a combination of multiple words, or an entire phrase. For simplicity, this article uses the term keyword to refer to all three types.
關鍵詞密度（keyword density）也被稱為搜索項密度（term density ），是關于特定搜索請求的項在網(wǎng)頁上所有項中的比率。例如，如果你想要的200 個詞的網(wǎng)頁就是關鍵詞“失眠癥”被找到，而你的網(wǎng)頁上這個詞出現(xiàn)了12 次，你網(wǎng)頁上這個詞的關鍵詞密度是6% （12/200）。搜索引擎通常認為有 6~7%關鍵詞密度的網(wǎng)頁是很高質(zhì)量的網(wǎng)頁。
Keyword density, also known as term density, is the ratio of items in a specific search request to all items on a web page. For example, if the 200 word web page you want is the keyword "insomnia" found, and the word appears 12 times on your web page, the keyword density of the word on your web page is 6% (12 / 200). Search engines usually think that pages with 6-7% keyword density are high-quality pages.