What does Keyword Research mean?
Keyword in SEO means finding out the search term the viewers are searching on Google for getting information or insights.

Why do we need the search terms?
Consider that you have written content for your blog that covers all the topics, and you post it, now you are waiting for people to visit your blog but are not getting any views.

Why are you not getting viewers for your blog?
Because your website is not showing in the top results or the first page of the SERP because google doesn’t know that your blog has the content that can be helpful for the viewers.

How to get in the Top results of the searches?
Keyword research is one of the important steps that can help in getting your blog on the top searches of Google's Results.

We have to find the main topic or the core topic first for which we are going to write the content and later use as many related keywords that we can use in the blogs so that google understands what is in your blog.

Here I have shared some quick tips for keyword research for content marketing.

Google suggest
Google suggest is the best tool that shows you what the people are searching for.
Go to Google search.
Search for the topic you are going to write the content. 
Ex. "food in Jacksonville"
Type this search term in the google search and wait, you will see a lot of similar terms appearing below, these are the terms people are looking for.
For getting more useful suggestions make use of '_' before and after the term. You will find a lot of terms similar to your topic which you can use while writing your content.
Ex: "_ food in Jacksonville", "food in Jacksonville _"

People also ask
This is the other best suggestion we receive from google for getting keywords.
Search for your topic on Google,
Now after the first or second search result you will see a section called People also ask.
Here you will see a variety of different topics that people are looking for, answering these questions in your blog will help you rank better on Google.

Searches Related to...
Search related to is a search suggestion will find at the ending of the page.
These are the results that people are searching for which will help you in ranking your content on Google.

Look at keywords your competitor is targeting
See what your competitor is doing, see what keywords is your competitor ranking on.
Use some free tools like Ubersuggest.
Here you can get the complete analysis of the website and you will see the organic keywords, monthly traffic, domain authority, backlinks, etc.
You will see the top running blogs of the website and their targeted keywords.

Long-tail keywords
Long-tail keywords are keywords that tell the search intent of the searcher. 
For Ex. Normal Keyword: "Jacksonville SEO" - This is a broader keyword we can't tell the intent of the searcher.
Long-tail keyword: "Best SEO company in Jacksonville Fl" - This keyword tells us exactly what the searcher wants, so it becomes easy to write content around this topic.

Use Answer the Public
Answer the public is a keyword tool that is used to visualize and suggest questions that people may ask.
This can help us browsing many questions that would be asked by people.
It provides a large variety of topics that we can consider using in our blog.

Use Google Trends
Google Trends is a website by Google that analyzes the popularity of the topic in google across various regions.
This helps us understand that if the keyword we are using worth using this.
Enter the topic in the Google Trends search.
After hitting Enter you will see the popularity of the topic over different periods.
Scroll down and you will find related queries regarding the topic which can be useful for ranking your content.

Google Keyword Planner
Keyword Planner is an amazing tool that tells the exact searches for the keyword and its difficulty for ranking, it suggests a number of the related keyword to the topic with their search volume.
We have to search for keywords that are high search volume and less difficult to rank.

Conclusion:
I hope you have got to know about a lot of things regarding keyword research for content writing that will help you rank your content on google.

One last tip:
Try to find topics that surround your main topic instead of going out of the line. This will help you get viewers who are familiar with your topics or they will bounce back if the things don't connect.