 Oscilloscope probes can change how they see signals with the flick of a switch. That little X1, X10 slide switch lets you change the probe's attenuation as needed. Just be sure to change its accompanying setting on the scope when you do, or the scope measurements will be all wrong. For most common usage, X10 is your best bet. This setting allows only one tenth of the original signal to pass, and allows us to view higher frequency signals and minimize loading effects where the probe's presence might otherwise distort your circuit signal. Switching to X1 turns that attenuation fully off, and allows the scope to connect directly to the full test signal. This is helpful when you need to measure very low amplitude signals, which may be reduced below the signal floor when using X10. But with no attenuation, the probe's capacitance can influence the circuit, and prevent reliable measurement at high frequencies.