This means:
“The post claims to explain why someone may constantly have phlegm or mucus in their throat and what can be done to reduce it.”
Breakdown
“The real causes” = promises to reveal the underlying reasons for persistent mucus.
“Constant phlegm and mucus” = ongoing throat mucus or the frequent need to clear your throat.
“How to get rid of it” = promises remedies or treatments for the problem.
Common causes
Persistent throat mucus can be associated with postnasal drip, allergies, respiratory infections, acid reflux, asthma, smoking, or environmental irritation. Sometimes the sensation comes from throat irritation rather than excessive mucus production.
Important point
This is health-information clickbait because “the real causes” makes it sound as though there is one hidden explanation, when there can be many.
If mucus persists or is accompanied by difficulty breathing, chest pain, coughing up blood, unexplained weight loss, or a high fever, medical evaluation is appropriate.
A more accurate version:
“Why you may have persistent throat mucus and what can help relieve it.”
