"Heart Failure" is a common term meaning a lot to the layman but covering a multitude of diagnoses ans "sins". We ALL die of heart failure.
To the medical profession, it is far more complicated and can be divided up into many headings the main ones being Right sided heart failure ( Congestive Cardiac Failure as mentioned by 237SJ) and (Left sided heart failure) as indicated by Peter Pedant) and no answer is complete without the NHS website of Buenchico.
\\\Would you be treated for this,\\ almost certainly.
\\\\or does it come on suddenly,\\ Left sided heart failure comes on suddenly but right sided (congestive cardiac failure) comes on gradually.
So for the layman "Heart failure " means whatever you want it to mean....but to the professional it is something more specific.
Today the most commonest cause of heart failure is congestive cardiac failure, brought on by the explosion of obesity, alcohol and drug abuse, Type 2 diabetes and hypertension ( high blood pressure) not forgetting coronary artery disease.