Low-frequency transformers are used to propagate signal voltage and signal power, and are also used to achieve impedance matching between circuits, with isolation function.
In general, low-frequency transformers refer to "power frequency transformers" used to change the voltage below (50 Hz), and the iron core is generally a silicon steel sheet with high magnetic conductivity.
High-frequency transformers refer to transformers that operate at high frequencies as energy changes. Due to the high frequency of the magnetic field, the silicon steel sheet will produce eddy currents (the conversion speed of the small magnet in the silicon steel sheet cannot keep up), so the high-frequency transformer generally uses "high-frequency ferrite" as the magnetic core.
There is no difference in principle between high-frequency transformers and low-frequency transformers, but due to the different frequencies of high-frequency and low-frequency, the iron core used for transformers is also different.