Types of Machine Learning/Data Analysis
You can use ML/DA in almost every sector, but to generalise there are few domains which i would like to list

Broadly it is classified based on data


Text data
Image data
Signal/Periodic Data
Financial data/Numbers


In here we can further classify or give names to the domains. Text data broadly falls under Natural Language Processing (NLP). Here you can work with text generation, text segmentation, document classification, chatbots, topic modelling, Summary extraction &amp; much more
NLP Research,
NLP Application I have added links to 2 articles listing current research &amp; applications by current industry standards. 

Image data is broadly falls under Computer vision. Here you work with videos, live streams, images. They can be satellite images, road accidents, machine parts etc. You can do analysis of football match, or even do analysis on plastic pollution in oceans. Sub topics can be classified as 


Image tagging
Image based information gathering
Object prediction
Vision based health prediction
Biological researches
Image rectification using NNs


And much more. If you want to have hands-on experience for image based data, please visit this site, here you will get basic idea of what topics one can achieve with image data.

Periodic data consists of measurements from machines, observations of how they work, it also includes biological data. Basically our normal signal processing or risk analysis. It's application is much needed for machinery makers, health sectors &amp; financial brokers, vehicle positioning etc. Anything which has some time based data into it can be used to simplify routes, analyse risks &amp; avoid unnecessary wear &amp; tear.

But generally this domains are used together with each other unless you go for research. Working for a solution firm i have encountered many projects where i had to gather text data from image &amp; use topic modelling for classification. Had a project where i had to analyse data generated from video cam observing human to predict their HR for next few seconds.

Hope this helps you in identifying what domain interests you more.