A Data Tracker is more likely to refer to the digital "cookies" or "tracking cookies" that advertisements and websites deposit in your browser to follow and report back to them what sites you visit, and your browsing habits. Tracking cookies are generally what make the web feel either convenient or creepy.
A Data Broker is a "third party" business that sells user data aggregated from many sources (subscriptions, warranty registrations, supermarket and department store loyalty cards, browsing habits) to other businesses. Their data is usually stripped of personal data, but not always.
Do Not Track is a snippet of code that your browser can send to websites to request that they not use tracking methods to watch your browsing habits. It is a standardized method that all websites can look for, but none are required to honor. There is no law in the US that states a website must not track your activity.
Cookies are generally useful bits of code, allowing for settings to persist for you across reboots and logins. For example, when you ask the weather site to remember your zip code, but don't ever create a login or allow it to track your location, it is a cookie in the browser or app that stores that info. Next time you go to the weather site, it reports back your zip code and loads your local weather without asking. Convenient or creepy?
That leads us to Tracking Cookies. Symantec defines them as: "...a specific type of cookie that is distributed, shared, and read across two or more unrelated Web sites for the purpose of gathering information or potentially to present customized data to you." (https://www.symantec.com/security-center/writeup/2006-080217-3524-99) It is these tracking cookies that act under the radar and can gather data about your habits even when you are not logged into any sites you are browsing, or the search engine, or even the computer you are using. Data brokers can still build up a generic picture of you that is highly unlikely to identify you personally, but can help them collect aggregate data about browsing habits.
Privacy enhancements to assist in reducing tracking are available. They exist as alternative search engines you can use like DuckDuckGo that don't store or track your search history in any way, browser extensions like Privacy Badger that watch web traffic for tracking activity and block domains that engage in that activity, mobile apps like AdBlock Plus that can stop advertisements in Safari on iPhones or can be used as an alternative browser on other platforms. Other mobile browsers are available such as Brave and DuckDuckGo that incorporate anti-tracking and other privacy enhancing features by default.